Bright nickel plating



United States 2,980,595 BRIGHT NICKEL PLATING a K.Sanicky, Cleveland, Ohio, assignor to Incar, lnc.

No'Drawing. Filed Aug. 11, 1958, Ser. No. 754,142

' Claims. (Cl. 204-49 numerous brighteners have enjoyed commercial success because of their limitations and the rapidly increasing demands of modern commercial platers for absolute uni forniity in appearance of bright nickel plate over a 'wide variety of very irregularly shaped surfaces. Such require ments demand a brightener that will give the necessary uniformity of brightness over a very wide range of cathode current densities, and moreparticularly at the very low but undetermined current densities encountered in the recesses and crevices of some of the more drastically recessed surfaces of articles that must be bright nickel plated. It is also true that'such uniformly bright" deposits must also have the other desirable physical properties such as adherence, ductility, freedom from pits and, pores and .ability to take. a bright chrome plate,

without which no bright nickel plate can hope to enjoy commercial success. Mostof the multitude of nickel plating brighteners can be put in either one of two classeslas adequately dis cussed in the second edition of ModernElectroplating (1953) pages 31l3l5inclusive. The first class usually referred to as primarybrighteners consists of thosecom-.

pounds which have in the molecular structure a group. It is the function ofsuitable compounds of this class, when added to a nickel plating bath, to produce a basically bright-nickelplate, hence they are sometimes referred to as basic .brighteners. Some representative brighteners of this class. comprise the aryl sulfonic acids and sulfonates such as the mono, di and tri sulfonates of the benzene and naphthalene series of compounds, as dis-, closed forexarnple in US. Patents 1,818,229; 1,972,693; 2,112,818; 2,114,006; 2,125,229; and 2,401,428, among others. Some other sub-classes of primary or basic brighteners of this first general class are the aryl sulfonamides and sulfonimides of US. Patents 2,191,813 and 2,466,677; the aryl sulfinic acids of US. Patent 2,402,801; and the arylsulfone sulfonates of US. Patent 2,467,580 forexample.

While the primary or basic brighteners of the first class produce semi-bright plate at the current densities used in commercial nickel plating, the brilliance of the deposit so produced is not usually sufiicient to meet the demands of platers, particularly where chromium is to be plated over J atent O bright nickel, hencethe brighteners of the second class were developed.

The brighteners of the second class improve the luster of bright deposits from baths containing brighteners of the first class and act synergistically with them to extend the range of current densities over which uniformly bright nickel deposits can be obtained. It is for these reasons that the brighteners of the second class are usually referred to as secondary or booster brighteners, however, because of some confusion in the literature or brightener nomenclature, the brighteners of the second class so defined will be referred to herein as booster brighteners or boosters. The subclasses of the booster brighteners of the second class are too numerous and complicated to outlinehere, but an adequate discussion can be found in Modern Electroplating" referred to above.

Mostof the brighteners disclosed in the more recent patents are those of the second class, or boosters. Although a great many compounds have been disclosed, only a very few have met with commercial acceptance. This is because of the increasing complexity in the shape of articles of modern design that have to be finished by bright nickel plating followed by chromium plating. The principal defect of most booster brighteners, including some of those in commercial use today, is failure to provide a truly uniformly bright plate over the entire surface .of an irregularly shapedfobject, or more specifically,

failure to pr'ovidea bright plate in the innermost recesses of such surfaces. 7 Indeed, some of the otherwise-best boostersfail to'deposit any plate at all in the bottom of some recesses, while a more common fault is found in those which cause deposits in such recesses to turn dark or black during the plating process. There is therefore an urgent need in the bright nickel platingindustry for a booster brightener that willprovide a; plate that is uniformlybright over the entire surface of recessed objects, particularly in the recesses, and at the same time possess all the required physical properties of commercial bright nickel such as adherence, ductility, and ability'to take bright chromium plate directly. It is an object of this invention to supply this need.

Among the multitude of booster brighteners that have been proposed are the alkylene polyamines. While these compounds, when used in nickel plating bath containing suitable primary brighteners of the first class, produce nickel deposits of adequate ductility, they do not provide the brilliance demanded by modern commercial electroplaters. Means for overcomingthis defect have been proposed, as for example, increasing the molecular weight of the alkylene polyamines by combining them with various substances. Such reaction products usually produce brighter nickel plates than the unreacted alkylene poly-' amines, but these plates are likely to be less ductileand tend to be dark in the low current density areas of recessed surfaces, particularly when the reaction products areused as booster brighteners with primary brighteners of the sulfonimide sub-class, such as saccharin for ex,- ample. Some of the reaction products of alkylene polyamines that product the brightest nickel plate fail ,to deposit any nickel at all in the lowest current density areas at the bottom of recessed surfaces.

I have now found that by reacting alkylene polyamines with alcohol chlorides so as to substitute all the hydrogen of the amino groups with hydroxyalkyl groups to produce totally hydroxyalkylated alkylene polyamines, booster brighteners are produced that have all of the desirable qualities and none of the defects of other reaction products of alkylene polyamines, and in addition, possess virtues not found in theseother products. The totally hydroxyalkylated alkylene polyamines, when used'singly or in combination as booster brighteners in nickel plating baths containing suitable primary brighteners of the first;

class, produce bright nickel plates of high brilliance over a very wide range of current densities, so that bright plate is obtained in the bottom .of recesses and crevices of irregularly shaped surfaces with no tendency toward dark or discolored plate or toward unplated areas. In addition, such plates possess all the other desirable properties of bright nickel plate, such as ductility, adhesion. to; basis metal, uniformity, freedom from pits and other surface defects, and good chromability; i.e., the property of accepting chromium plate without sacrifice of brilliance or any other desirable property. 7

Another virtue of the totally hydroxyalkylated alkylene polyamines is that they also possess anti-pit properties in the nickel plating bath, thus avoiding the necessity for using the usual wetting agents generally added tobright nickel plating baths to avoid pitting, to which such baths are commonly addicted. Moreover, the totally hydroxylated alkylene polyamines are completely compatible with the wetting or anti-pit agents generally used commercially, such as the higher alcohol sulfates,so that no problems are encountered in cases where such wetting or anti pit agents are habitually used, thus making it possible for the plater to follow custom and use, such agents if he so desires, or to convert from an older process to the new process of this invention. In other words, the use of conventional wetting or anti-pit agents such as the higher alcohol sulfates is optional with bright nickel plating baths containing totally hydroxyalkylated alkylene polyamines as booster brighteners. a

The totally hydroxyalkylated alkylene polamines of.

this invention can be made byreacting them with'alcohol chlorides, such as ethanol chloride or propanol chloride for example, following conventional and well-known procedures and in such proportions that all of the amino hydrogen is substituted by hydroxyalkyl groups, leaving no free amino hydrogen. Examples of the totally hydroxyalkylated alkylene polamines that have been found to be particularly efiective when used as booster brighteners in a nickel plating bath containing one or more suitable primary brighteners are:

Pentahydroxyethyl diethylene triamine Pentahydroxypropyl diethylene triamine Hexahydroxyethyl triethylene tetramine 'Hexahydroxypropyl triethylene tetramine Heptahydroxyethyl tetraethylene pentamine Heptahydroxypropyl tetraethylene pentamine These totally hydroxyalkylated alkylene polyamines may be used singly or in combination as the booster brightener constituent of nickel plating baths contain- The primary brightener of the first class to be used with these new boosters may be selected as desired from.

the list of patents previously cited. The most commonly used primary brighteners in commercial bright nickel plating are the aromatic sulfonic acids or sulfonates and the sulfonamides and sulfonimides of benzene, andtoluene. Specifically it has been found that the naphthalene disulfonates are probably the best of their type while.

benzosulfimide or saccharin as such, or more conveniently in the form of its sodium salt. and para toluene sulfonamide are the best of their type and all function well as primary brighteners of the first class with the W well known in the prior art and the formulae for which are available in numerous publications. :Such baths contain in solution the sulfate, chloride, sulfamate or fluoborate of nickel or combinations thereof in various proportions, together with boric acid.

As illustrative examples of complete embodiments of this invention the following typical bright nickel plating bath formulations may be cited:

Bath I: Grams per liter Nickel sulfate, NiSO -6H O 250.0 Nickel chloride, NiCl -6H O 60.0 Boric acid, H BO Saccharin or saccharin, sodium salt 40 Heptahydroxypropyl tetraethylene pentamine 0.01

Bath II: I

Nickel sulfate, NiSO -6H O 300.0 Nickel chloride, NiCl -6H O Boric acid, H BO 45.0 Naphthalene disulfonic acid 5.0 Hexahydroxyetltyl triethylene tetrarnine 0.005 Hexahydroxypropyl triethylene tetramine 0.005

The operating conditions commonly used in bright nickel plating and which .are well known in the art are satisfactory for the above baths and for example,.may be as follows:

Range Preferred Tern perature -4-.. Current density 5-110 amps/sq. (15.... 45-60 amps/sq. it.

Can be increased% with air agitation It is understood that a suitable wetting or anti-pit" agent may be added to either of the above formulations if desired. The commonly accepted practice is to use about 0.25 gram per liter of lauryl alcchol sulfate if desired.

It will also be understood that any suitable primary brightener of the first class as previously defined and selected as desired from the references given may be used instead of the naphthalene disulfonate or the saccharin of the above examples, and that the amounts of such primary brighteners of the first class to be used as well as the amount of the totally hydroxyalkylated alkylene polyamine booster brightener will be selected so that the two types of brighteners act synergistically to produce a unifirmly bright nickel plate. In general it will be found necessary to use a concentration of at least 0.5 gram per, liter of the primary brightener of the first class and a concentration of at least 0.001 gram per liter of the totally hydroxyalkylated alkylene polyamine booster brightener. Higher concentrations than these minimaare generally used, if desired, providing the solubilities of the compounds selected permit. Upper limits are, in

general, not critical.

What is claimed is:

1. A bright nickel plating bath containing a primary brightener of the first class selected from the group consisting of aryl sulfo namides, aryl sulfinimides, aryl sul-' finic acids and arylsulfone sulfonates, and from about 0.001 to 0.1 gram per liter of a totally hydroxyalkylated alkylene polyamine having 3 to 5 nitrogen atoms as a booster.

polyamine having 3 to 5 nitrogen atoms as a booster.

3. A bright nickel plating bath containing a primary brightener of the first class selected from the group consisting of aryl sulfonamides, aryl sulfinimides, aryl sulfinic acids and arylsulfone sulfonates, together With from about 0.001 to 0.1 gram per liter of a totally hydroxyalkylated alkylene polyamine having 3 to 5 nitrogen atoms as a booster.

4. A bright nickel plating bath containing at least 0.5 gram per liter of a naphthalene sulfonate and from about 0.001 to 0.1 gram per liter of heptahydroxypropyl tetraethylene pentamine.

5. A bright nickel plating bath containing at least 0.5 gram per liter of saccharin and from about 0.001 to 0.1 gram per liter of heptahydroxypropyl tetraethylene pentamine.

6. A process for producing uniformly bright nickel deposits which comprises electrodepositing nickel from an aqueous acidic plating bath containing at least one nickel salt, a primary brightener of the first class selected from the group consisting of aryl sulfonamides, aryl sulfinimides, aryl sulfinic acids and arylsulfone sulfomates, and from about 0.00 l to 0.1 gram per liter of a totally hydroxyalkylated alkylene polyamine having 3 to 5 nitrogen atoms as a booster.

7. A process for producing uniformly bright nickel deposits which comprises electrodepositing nickel from an aqueous acidic plating bath containing at least one nickel salt, as a primary brightener, an aryl sulfonate from about 0.001 to 0.1 gram per liter of a totally it? hydroxyalkylated alkylene polyamine having 3 to 5 nitrogen atoms as a booster.

8. A process for producing uniformly bright nickel deposits Which comprises electrodepositing nickel from an aqueous acidic plating bath containing at least one nickel salt, a primary brightener of the first class selected from the group consisting of aryl sulfonamides, aryl sulfinimides, aryl sulfinic acids and arylsulfonic sulfonates together with from about 0.001 to 0.1 gram per liter of a totally hydroxyalkylated alkylene polyamine having 3 to 5 nitrogenatoms as a booster.

9. A process for producing uniformly bright nickel deposits Which'comprises electrodepositing nickel from an aqueous acidic plating bath containing at least one nickel salt, at least 0.5 gram per liter of a naphthalene sulfov mate and from about 0.001 to 0.1 gram per liter of hep- I tahydroxypropyl tetraethylene pentamine.

References Cited in the file of this patent UNITED STATES PATENTS 2,662,863 Ellis Dec. 15; 1953 2,773,818 Moy et a1. Dec. 11, 1956 2,833,705 Winters May 6, 1958 2,836,549 Nobel et al. May 27, 1958 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent, No. 2380, 595 April 18 1961 Marilyn K, 4 Sanicky he above numbered pat- It is hereby certified that error appears in t Patent should read as ent requiring correction and that the said Letters corrected below.

line 59 for 'product" read produce for in aryl sulfonate" read we an. aryl sulfonate and column 5, line 29 after "sulfonate" insert and column 6 line 27, list of references cited for the patent number "-2 662,863" read 2 662 853 Column 2, column 4 line '73,

Signed and sealed this 12th day of September 1961.

(SEAL) Attest: ERNEST W. SWIDER DAVID L. LADD Commissioner of Patents Attesting Officer 1 USCOMM-DC 

1. A BRIGHT NICKEL PLATING BATH CONTAINING A PRIMARY BRIGHTENER OF THE FIRST CLASS SELECTED FROM THE GROUP CONSISTING OF ARYL SULFONAMIDES, ARYL SULFINIMIDES, ARYL SULFINIC ACIDS AND ARYLSULFONE SULFONATES, AND FROM ABOUT 0.001 TO 0.1 GRAM PER LITER OF A TOTALLY HYDROXYALKYLATED ALKYLENE POLYAMINE HAVING 3 TO 5 NITROGEN ATOMS AS A BOOSTER. 